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Process for producing non-flammable quasi-solid electrolyte and electrolyte-separator for lithium battery applications

a lithium battery and quasi-solid electrolyte technology, applied in the direction of non-aqueous electrolyte cells, cell components, electrochemical generators, etc., can solve the problems that electrochemists and battery designers have not considered possible or desirable, and achieve the effect of preventing potential li metal dendrite internal short circuit and thermal runaway problems, simple and easy-to-implement approach, and low electric and ionic conductivities

Active Publication Date: 2015-01-22
GLOBAL GRAPHENE GRP INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent text describes a new technology that can effectively prevent the flammability of organic solvents used in batteries. This is achieved by adding a high amount of a lithium salt to the solvent to form a solid-like or quasi-solid electrolyte. The resulting electrolyte has a vapor pressure that is too low to ignite, and any accidentally initiated flame does not sustain for longer than a few seconds. This technology could potentially reshape the landscape of the electric vehicle industry. The patent also mentions that using more volatile solvents can increase the effective concentration of the lithium salt.

Problems solved by technology

We have also routinely achieved an ultra-high lithium salt concentration higher than 9-11M, which have not been considered possible or desirable by electrochemists and battery designers.

Method used

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  • Process for producing non-flammable quasi-solid electrolyte and electrolyte-separator for lithium battery applications
  • Process for producing non-flammable quasi-solid electrolyte and electrolyte-separator for lithium battery applications
  • Process for producing non-flammable quasi-solid electrolyte and electrolyte-separator for lithium battery applications

Examples

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example 1

Some Examples of Electrolytes and Electrolyte-Separator Layers Used

[0148]A wide range of lithium salts can be used as the lithium salt dissolved in an organic liquid solvent (alone or in a mixture with another organic liquid or an ionic liquid). The following are good choices for lithium salts that tend to be dissolved well in selected organic or ionic liquid solvents: lithium borofluoride (LiBF4), lithium trifluoro-metasulfonate (LiCF3SO3), lithium bis-trifluoromethyl sulfonylimide (LiN(CF3SO2)2 or LITFSI), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LiBF2C2O4), and lithium bisperfluoroethy-sulfonylimide (LiBETI). A good electrolyte additive for helping to stabilize Li metal is LiNO3. Particularly useful ionic liquid-based lithium salts include: lithium bis(trifluoro methanesulfonyl)imide (LiTFSI).

[0149]Preferred organic liquid solvents include: ethylene carbonate (EC), dimethyl carbonate (DMC), methylethyl carbonate (MEC), diethyl carbonate (DEC), propylene c...

example 2

Vapor Pressure of Some Solvents and Corresponding Quasi-Solid Electrolytes with Various Lithium Salt Molecular Ratios

[0152]Vapor pressures of several solvents (DOL, DME, PC, AN, with or without an ionic liquid-based co-solvent, PP13TFSI) before and after adding a wide molecular ratio range of lithium salts, such as lithium borofluoride (LiBF4), lithium trifluoro-metasulfonate (LiCF3SO3), or bis(trifluoro methanesulfonyl)imide (LiTFSI), were measured. Some of the vapor pressure ratio data (ps / p=vapor pressure of solution / vapor pressure of solvent alone) are plotted as a function of the lithium salt molecular ratio x, as shown in FIG. 2-5, along with a curve representing the Raoult's Law. In all cases, the vapor pressure ratio follows the theoretical prediction based on Raoult's Law for up to xs / p value, the vapor phase of the electrolyte either cannot ignite or cannot sustain a flame for longer than 3 seconds once initiated.

example 3

Flash Points and Vapor Pressure of Some Solvents and Corresponding Quasi-Solid Electrolytes with a Lithium Salt Molecular Ratio of x=0.3

[0153]The flash points and vapor pressures of several solvents and their electrolytes with a lithium salt molecular ratio x=0.3 are presented in Table 1 below. It may be noted that, according to the OSHA (Occupational Safety & Health Administration) classification, any liquid with a flash point below 38.7° C. is flammable. However, in order to ensure safety, we have designed our quasi-solid electrolytes to exhibit a flash point significantly higher than 38.7° C. (by a large margin, e.g. at least increased by 50° and preferably above 150° C.). The data in Table 1 indicate that the addition of a lithium salt to a molecular ratio of 0.35 is normally sufficient to meet these criteria.

TABLE 1The flash points and vapor pressures of select solvents and theirelectrolytes with a lithium salt molecular ratio x = 0.3.FlashFlash pointVapor pressurepoint(° C.) w...

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Abstract

A process for producing a separator-electrolyte layer for use in a lithium battery, comprising: (a) providing a porous separator; (b) providing a quasi-solid electrolyte containing a lithium salt dissolved in a first liquid solvent up to a first concentration no less than 3 M; and (c) coating or impregnating the separator with the electrolyte to obtain the separator-electrolyte layer with a final concentration ≧the first concentration so that the electrolyte exhibits a vapor pressure less than 0.01 kPa when measured at 20° C., a vapor pressure less than 60% of that of the first liquid solvent alone, a flash point at least 20 degrees Celsius higher than a flash point of the first liquid solvent alone, a flash point higher than 150° C., or no detectable flash point. A battery using such a separator-electrolyte is non-flammable and safe, has a long cycle life, high capacity, and high energy density.

Description

FIELD OF THE INVENTION[0001]The present invention provides a non-flammable electrolyte composition and electrolyte-separator layer for use in a secondary or rechargeable lithium battery.BACKGROUND[0002]Rechargeable lithium-ion (Li-ion), lithium metal, lithium-sulfur, and Li metal-air batteries are considered promising power sources for electric vehicle (EV), hybrid electric vehicle (HEV), and portable electronic devices, such as lap-top computers and mobile phones. Lithium as a metal element has the highest lithium storage capacity (3,861 mAh / g) compared to any other metal or metal-intercalated compound as an anode active material (except Li4.4Si, which has a specific capacity of 4,200 mAh / g). Hence, in general, Li metal batteries (having a lithium metal anode) have a significantly higher energy density than lithium-ion batteries (having a graphite anode).[0003]Historically, rechargeable lithium metal batteries were produced using non-lithiated compounds having relatively high speci...

Claims

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Application Information

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IPC IPC(8): H01M10/0566H01M10/0568H01M10/0569H01M2/14H01M50/403H01M50/411
CPCH01M10/0566H01M10/0569H01M2300/0028H01M2/145H01M2300/0025H01M10/0568C08J5/18H01M2/162Y02E60/10H01M50/44H01M50/403
Inventor HE, HUIJANG, BOR Z.WANG, YANBOZHAMU, ARUNA
Owner GLOBAL GRAPHENE GRP INC
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